[isp-dns] Re: is reverse dns mandatory?

["R. Scott Perry" <horizons@...]

> I've got a consulting client who's subletting some colo space.  The
> company he's dealing with will neither do reverse dns for him, nor will
> they give it to him to do.
>
> They say it's unnecessary.
Recommend the client switch to a better Internet provider.

> So far we haven't seen any problems, but we know we may in the future,
> with email, and perhaps with some ftp and/or ssh logins.
You definitely will.  AOL for years has treated a missing reverse DNS entry 
as a very high indicator of spam (in their undocumented spam control 
system, which silently deletes E-mail).  AOL more recently has started 
saying that they may reject connections based on the lack of a reverse DNS 
entry.

> Looking through various threads on various lists and newsgroups, and
> through the RFCs, it appears as if reverse DNS is NOT mandatory.
RFC1912 2.1 says "Every Internet-reachable host should have a name... Many 
services available on the Internet will not talk to you if you aren't 
correctly registered in the DNS" (referring to reverse DNS 
entries).  Although that isn't "SHOULD" (all caps), it seems to be the same 
as "SHOULD" (which in RFC terms essentially means "You must do this unless 
you [1] have a reason to do otherwise, and [2] are willing to accept the 
consequences").

So the RFCs definitely say that the company should provide reverse 
DNS.  They technically aren't required to per the RFCs, but then again, 
technically nobody is forced to follow the RFCs.

                                                   -Scott
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